Porphyrin-based covalent organic framework coated stainless steel fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons in water and soil samples

A porphyrin-based covalent organic framework (COF) was synthesized via a Schiff base reaction between tetra (4-aminophenyl) porphyrin and 4,4'-biphenyldicarboxaldehyde. The porphyrin-based COF was physically coated on stainless steel for headspace solid-phase microextraction (HS-SPME) of polycyclic aromatic hydrocarbons (PAHs) prior to their determination by gas chromatography-flame ionization detection (GC-FID). Some properties of the prepared fiber like morphology, structure and stability were tested. The effective parameters including extraction temperature, extraction time, NaCl concentration, agitation speed, desorption temperature and desorption time on the performance by HS-SPME were optimized systematically. The study of extraction mechanism revealed the pi-pi stacking interaction between porphyrin-based COF fiber and PAHs. Under optimum condition of the developed method, a wide linear range (1-150 ng mL(-1)) with high determination coefficient (R-2 > 0.99), low detection limit (0.25 ng mL(-1)) and low quantitation limit (0.5 ng mL(-1)) were obtained. The repeatability (one fiber, n = 3) and the reproducibility (fiber-to-fiber, n = 3) expressed as the relative standard deviations (RSDs) were in the range of 0.27%-1.75% (intra-day), 2.73%-6.69% (inter-day) and 3.34%-8.62% (fiber-to-fiber), respectively. The developed porphyrin-based COF HS-SPME method had been applied for the determination of PAHs in water and soil samples with satisfactory recoveries in the range of 67.87%-98.74%, 41.13%-104.76%, respectively.